The knife tool won't show the exact result that was done before pressing enter
Congrats. You've encountered a weird limitation of the Knife Tool.
It acts up with too large near/far clipping range.

Unexpected behavior with extreme clipping range (0,1mm-1000000mm)


Solution 01
Adjust your clipping range
Lower the highest values, until the knife tool starts working correctly.



Solution 02
Use flat orthographic view.
Knife tool works fine even with extreme clipping values, when using front/top/side orthographic view.



Note
This is actually caused by 3D View limitations that all OpenGL/DirectX graphics applications have. It's not just a Blender thing.
You can read more about it in the Blender Troubleshooting Manual.